binary-search

I am looking for an efficient formula working in Java which calculates the following expression: (low + high) / 2 which is used for binary search. So far, I have been using "low + (high - low) / 2" and "high - (high - low) / 2" to avoid overflow and underflows in some cases, but not both. Now I am looking for an efficient way to do this, which would for for any integer (assuming integers range from -MAX_INT - 1 to MAX_INT). UPDATE : Combining the answers from Jander and Peter G. and experimenting a while I got the following formulas for middle value element and its immediate neighbors: Lowest

I have an array of hex numbers, and I need to go over other numbers and check if they appear in that array. Right now i'm using a foreach loop that goes over the entire array each time. Is there a way to make it faster by sorting the array at first, and then implementing binary search on it. The code at the moment: sub is_bad_str{ my ($str, @keys) = @_; my $flag = 0; my ($key, $hex_num); if ($str =~ m/14'h([0-9a-f][0-9a-f][0-9a-f][0-9a-f])/;){ #'# fixes bad highlighting $hex_num = $1; } if (defined $hex_num){ foreach $key (@keys){ if ($hex_num =~ /\Q$key\E/i){ $flag = 1; last; } } } if (($flag

I was asked if a Binary Search is a divide and conquer algorithm at an exam. My answer was yes, because you divided the problem into smaller subproblems, until you reached your result. But the examinators asked where the conquer part in it was, which I was unable to answer. They also disapproved that it actually was a divide and conquer algorithm. But everywhere I go on the web, it says that it is, so I would like to know why, and where the conquer part of it is? Kenci The book Data Structures and Algorithm Analysis in Java, 2nd edtition, Mark Allen Weiss Says that a D&C algorithm should have

Every programmer is taught that binary search is a good, fast way to search an ordered list of data. There are many toy textbook examples of using binary search, but what about in real programming: where is binary search actually used in real-life programs? Binary search is used everywhere . Take any sorted collection from any language library (Java, .NET, C++ STL and so on) and they all will use (or have the option to use) binary search to find values. While true that you have to implement it rarely, you still have to understand the principles behind it to take advantage of it. Binary search

The great findInterval() function in R uses left-closed sub-intervals in its vec argument, as shown in its docs: if i <- findInterval(x,v) , we have v[i[j]] <= x[j] < v[i[j] + 1] If I want right-closed sub-intervals, what are my options? The best I've come up with is this: findInterval.rightClosed <- function(x, vec, ...) { fi <- findInterval(x, vec, ...) fi - (x==vec[fi]) } Another one also works: findInterval.rightClosed2 <- function(x, vec, ...) { length(vec) - findInterval(-x, -rev(vec), ...) } Here's a little test: x <- c(3, 6, 7, 7, 29, 37, 52) vec <- c(2, 5, 6, 35) findInterval(x, vec)

Based on the following definition found here Returns an iterator pointing to the first element in the sorted range [first,last) which does not compare less than value. The comparison is done using either operator< for the first version, or comp for the second. What would be the C equivalent implementation of lower_bound(). I understand that it would be a modification of binary search, but can't seem to quite pinpoint to exact implementation. int lower_bound(int a[], int lowIndex, int upperIndex, int e); Sample Case: int a[]= {2,2, 2, 7 }; lower_bound(a, 0, 1,2) would return 0 --> upperIndex is